Sensors, so-called thermo elements, with whose aid temperatures, among other things, can be measured are already known. Known thermo elements are made up of two materials, which have different characteristics and are connected to each other. These different materials generate between their open ends a voltage that is a function of the temperature differential. Thermo elements do not measure the absolute temperature but generate an output voltage which corresponds to a temperature difference or a temperature gradient between contact point and open end. This voltage (Seebeck voltage) is caused by the so-called Seebeck effect.
The described electrical Seebeck voltage is produced by thermo diffusion flows. A specific temperature means that the thermal energy stored in the material is distributed to the kinetic energy of the electrons and the vibrational energy of the atomic cores. In this case the ratio is a constant that is typical for the individual material. The electrons consequently have higher kinetic energy at the hot end than the electrons at the cold end of the conductor. The greater kinetic energy then causes the “hot” electrons to distribute more heavily in the conductor than the “cold” electrons. The result is a disequilibrium because the electron density increases at the cold end and decreases at the hot end. This happens for precisely the length of time it takes for the electric field generated by this disequilibrium to ensure that a state of equilibrium which counteracts the thermo-diffusion of the “hot” electrons comes about. The generated voltage Useebeck is defined by:Useebeck=α·ΔT with ΔT being the temperature differential between the conductor ends and α the Seebeck coefficient.
If a plurality of thermo elements is connected to each other by a series connection, then a thermopile is produced. This thermopile generates a higher voltage than an individual element depending on the number of interconnected thermo elements. Thermopiles are frequently used as infrared radiation detectors.
However, these known thermo elements have the disadvantage that the desired effect and additional parameters depend on the selected material pairing.